Robustness properties of sampled-data systems with dead time compensators

This study presents the development of dead-time compensator with Proportional Integral-Derivative (PID) controller and their implementation in real-time using the Programmable Logic Controller (PLC) on a heater-furnace system that constitute the temperature process. Though PID controller is effective to most of the processes, it has draw backs when used to control the processes with significant dead time. Therefore to eliminate the effects of long dead time, the dead-time compensator combined with PID is proposed. The control equation for the proposed dead time compensator is developed using the mathematical model of heater-furnace system and ladder logic program is created in GE Fanuc Versamax PLC. The PID controller is tuned using process reaction curve method and programmed in PLC. The proposed controller has an outer loop control mechanism with dead time compensator which feeds the inner loop PID controller. The effects of dead time on the performance of PID controller are eliminated through the outer loop control mechanism whose output does not contain modelling errors. The results of the proposed dead-time compensator with PID are compared with the results of the conventional PID controller without dead time compensation for both steady state response and servo-regulatory response. The results of the proposed controller show better improvement in the time domain specifications compared to conventional PID controller.

Paralleled inverters are widely employed in permanent magnet synchronous machine (PMSM) drives to increase system capacity and reliability. Due to the discrepancy of paralleled inverters, the differential-mode circulating current (DMCC) is a major concern in paralleled inverters fed PMSM drives. The DMCC would result in current unbalance and efficiency reduction. To address this issue, a low-frequency DMCC suppression considering dead time compensation is proposed in this paper, which can be effective in the suppression of both DMCC and zero-sequence circulating current. In detail, the DMCC due to the discrepancy of control settings such as dead time and switching period, is eliminated by a proposed dead time compensation. Besides, the DMCC owing to the hardware differences including device voltage drops, device turn-on/off delays and filter inductances etc., is suppressed by a proposed regulation of phase conduction time, being free of disturbing the command voltage of drive system. Finally, the effectiveness of the proposed method is experimentally validated under both two-level and three-level space vector modulations.

In this work we are interested in the stability and ℒ2-gain of hybrid systems with linear flow dynamics, periodic time-triggered jumps and nonlinear possibly set-valued jump maps. This class of hybrid systems includes various interesting applications such as periodic event-triggered control. In this paper we also show that sampled-data systems with arbitrarily switching controllers can be captured in this framework by requiring the jump map to be set-valued. We provide novel conditions for the internal stability and ℒ2-gain analysis of these systems adopting a lifting-based approach. In particular, we establish that the internal stability and contractivity in terms of an ℒ2-gain smaller than 1 are equivalent to the internal stability and contractivity of a particular discrete-time set-valued nonlinear system. Despite earlier works in this direction, these novel characterisations are the first necessary and sufficient conditions for the stability and the contractivity of this class of hybrid systems. The results are illustrated through multiple new examples.

For an inverter drive induction motor control system, a typical problem encountered is the nonlinear voltage gain caused by the non ideal characteristics of the power inverter. The switch dead time will introduce waveform distortion and fundamental voltage drop to the system. If not compensated, such distortions will introduce harmonic components which will cause additional loss in the induction machine. Therefore, the impact of harmonics caused by switching dead time are essential to induction motor drive design, especially when the motor is running at low speed. In this paper, a dead time compensation method is proposed. By adding a 6th order resonant controller to the existing current loop PI controller, the negative sequence 5th order and positive sequence 7th order current harmonics caused by the dead time are eliminated. The overall control scheme is implemented in synchronous rotating d-q reference frame. The controller resonant frequency is 6 times to the synchronous frequency, which is calculated with mechanical speed and slip. Experiment results of steady state and dynamic response studies are presented to validate the effectiveness of the proposed method.

Dead time compensation circuit for radiation detector

Anti-Jerk Control of a Parallel Hybrid Electrified Vehicle with Dead Time

In order to reduce voltage error and stator current distortion caused by dead time in the model predictive control (MPC). Based on the permanent magnet synchronous motor driver and model predictive current control (MPCC), an novel control algorithm is proposed to correct the negative influence caused by dead time to improve its steady-state performance of model predictive control. The correctness of the proposed algorithm is verified by simulation.

This work proposes an anti-windup structure for the ltered Smith predictor (FSP) which belongs to a class of dead-time compensators (DTCs). The proposed FSP structure does not use any extra tuning parameter due to the anti-windup characteristic. In addition stability analysis is presented based on describing function method to show robustness properties of the controller. Simulation results are used to compare the obtained solution with other anti-windup DTCs and a constrained model-based predictive controller (MPC). Experimental results on a neonatal intensive care unit are presented in order to shown the usefulness of the proposed controller.

Aiming at deficiencies of output voltage distortion and circulating current generation caused by dead-time effect in the modulation process, a simple and feasible dead time compensation strategy is presented. Firstly, the influence of dead-time effect on the output voltage of bridge is analysed, and a dead time compensation strategy is added between the modulation signal and dead time procession. According to the current direction of the bridge, the rising edge or falling edge of the driving signal is selectively delayed to compensate for dead-time effect. Secondly, an Optimized Triple Phase-shift (OTPS) modulation strategy is adopted with minimizing leakage inductor current Root-Mean-Square (RMS) control, which minimizes current stress, achieves soft-switching operation, avoids phase-shift errors caused by Dead-Time Effect, and optimizes control performance of DC-DC converters. Finally, simulated and experimental results are added to verify the correctness and effectiveness of the proposed method.

Single-photon avalanche diode (SPAD)-based light detection and ranging (LiDAR) introduces significant pileup errors at high echo photon flux due to the SPAD's dead time. To expand the application of single-photon LiDAR in the field of remote sensing, autonomous driving, etc., it is crucial to perform rapid and accurate ranging within an echo photon flux of a wide dynamic range. Emerging SPAD array detectors combined with specific photon detection modes attempt to strike a balance between photon detection efficiency and hardware resources, necessitating the development of appropriate dead time compensation methods. Therefore, we experimentally investigated a synchronous single-photon ranging LiDAR operating in a mode where up to two photons are detected per laser cycle, and proposed dead time compensation methods based on forward modeling of the photon detection process. The results show that, using a wide laser pulse of 3.5 ns, the compensated ranging error is less than 4.2 cm, while the uncompensated ranging error is as max as 17.96 cm. Our method provides a reference for dead time compensation in single-photon LiDAR that requires comprehensive consideration of detection efficiency and hardware resources.

This paper proposes a new dead time compensation method for a PWM inverter. Recently, PWM inverters are widely used for industrial applications, such as ac motor drives, distributed grid-connected systems and a static synchronous compensator (STATCOM). The nonlinear characteristics of the switch and the dead time cause a current distortion and a deterioration of the power quality. The dominant harmonics is the 5th and 7th harmonics in the stationary reference frame, and the 6th harmonics in the synchronously rotating frame. In this paper, a resonant controller which compensates the 6th harmonics in the synchronously rotating frame is proposed. This method does not require any off-line experimental measurements, additional hardware and complicated mathematical calculations. Furthermore it is easy to implement and does not cause any stability problem.

The distillation columns are widely used in various chemical industries. It is basically used for separating the components of a liquid mixture. The More volatile component is vaporized, and the less volatile one is left back in the liquid. The plant of distillation column that is considered in the present work is a SOPDT transfer function model imported from an online source. Due to the impact of present dead time, the stability in the output variable is a challenging task. So, the improved control performance is achieved by the dead time compensation using the Smith predictor. The PI control systems are designed, using MATLAB, for this plant with and without Smith predictor, and their performance is compared.

In networked control system, such as WirelessHART that is characterized by stochastic delay, the use of proportional integral and differential (PID) controllers is inadequate. This is because PID performs poorly in handling time-delay processes. The main reason for this poor performance is the limitation in the range of stable gain of the controller. Time delay causes oscillatory response of the PID with large gain. Likewise, sluggish response is experienced with small gain of the PID. Also, dead time compensators like smith predictor and internal model controller are difficult to be implemented practically since they require exact model of the process to be controlled. Therefore, this paper proposes the application of setpoint weighting strategy to be used alongside PID controller in a WirelessHART network. This method extends significantly the range of the PID gain, while providing good set point tracking and load regulation. From the simulation and experimental results obtained, the capability of the approach to load regulation and tracking can be seen in its fast recovery from effect of disturbance with minimal overshoot. Thus, a two degree of freedom control is achieved. Results also showed that the method is robust to real-time random variable network delay and model mismatches.

A novel manufacturing strategy based on continuous processing, integrated with online/inline monitoring tools, coupled with an advanced automatic feedback control system is highly desired for efficient Quality by Design (QbD)-based manufacturing of the next generation of pharmaceutical products with optimal consumption of time, space and resources. In this work, an advanced hybrid MPC-PID control system as well as a simpler PID controller for a direct compaction continuous tablet manufacturing process has been designed and implemented for a pilot-scale pharmaceutical process. An NIR sensor, an online NIR prediction tool, a PAT data management tool, an OPC communication protocol, a standard control platform and control hardware have been used to close the control loop. A systematic methodology to design and implement the control system has been also proposed. A control framework with features such as the option to run the plant in open-loop as well as in a closed-loop scenario has been developed. Furthermore, within the closed-loop scenario, options for a simpler PID, a dead time compensator (Smith predictor) as well as an advanced model predictive controller have been included. The feature to run the control strategy in simulation mode has been added to the control platform to facilitate virtual control system design and performance evaluation. Two case studies involving a direct compaction continuous tablet manufacturing process have been considered to demonstrate the closed-loop operation. Case Study 1 was completed at Rutgers University and constituted the use of a continuous cylindrical blender with a rotating screw. Case Study 2 was based on a continuous tumble mixer and was completed at the University of Puerto Rico—Mayaguez Campus (UPRM).

In this paper, a novel dead time compensation method is presented which produces inverter output voltages equal to reference voltages. The experimental result is also presented to demonstrate the validity of the proposed method. It shows that the compensation of the distorted voltage is possible up to sub-microsecond range. The reference voltage can be used as a feedback value, which is essential for sensorless vector control and flux estimation. The method is based on space vector PWM strategy and it can be carried out automatically by an inverter controller for initial set-up without any extra hardware. >